Catheters are tube-like members which are inserted into the body for diagnostic or therapeutic reasons. One of the therapeutic procedures applicable to the present invention is known as percutaneous transluminal coronary angioplasty ("PTCA"). PTCA can be used, for example, to reduce arterial buildup of cholesterol fats or atherosclerotic plaque. Catheters must have sufficient bending stiffness, kink resistance, and torsional rigidity to provide structural integrity for the catheter. The catheter must also be fluoroscopically visible or radiopaque so that the physician's catheter manipulation through the vasculature is facilitated. Further, it is necessary for the catheter, particularly the inner layer or "liner", to exhibit lubricity so that therapeutic devices can be easily passed through the catheter.
U.S. Pat. No. 5,061,738, issued to Solomon et al., discloses a medical article having a coating of an anticoagulant and a lubricant. The preferred lubricant is a non-curing silicone such as a polydialkylsiloxane. An antithrombogenic agent such as heparin is mixed with the lubricant and the mixture is then dissolved in a solvent. The medical article is immersed in the resulting composition of the antithrombogenic agent, the lubricant, and the solvent to coat the article. In the case where the article is a catheter, the lumen wall is coated by drawing the composition into the lumen by application of reduced pressure.
U.S. Pat. No. 5,084,315, issued to Karimi et al., discloses an article which becomes lubricious when wet which includes a base polymer and a coating composition. The coating composition is comprised of a lubricating polymer and a matrix polymer where the matrix polymer is selected so that it adheres to the base polymer and serves as a carrier for the lubricating polymer. The lubricating polymer is selected from a group of polymers which absorb water and are known as hydrophilics. A method of manufacturing is also disclosed where the base polymer and the coating composition are coextruded so that the coating composition is laminated on the surface of the base polymer.
U.S. Pat. No. 4,945,126, issued to Crosby et al., discloses a method of manufacture of a lubricant system which consists of a polymer matrix and a lubricant which comprises a blend of a polyolefin and finely divided polytetrafluoroethylene. The method involves the melt mixing of the polymer matrix and a lubricant using a process such as extrusion.
U.S. Pat. No. 5,254,107 issued to Soltesz, discloses a catheter comprising an inner plastic layer, a braided stainless steel fiber tubular member surrounding the inner plastic layer, and an outer tubular plastic layer. The braided stainless steel fiber tubular member is completely embedded in the outer tubular plastic layer along the length of the catheter.
It is an object of the invention to achieve catheter lubricity while providing structural integrity by providing a uniform coating of a lubricating polymer to the inner surface of the liner of the catheter such that bonding between the outer surface of the liner and adjacent layers is not compromised.
It is a further object of the invention to provide large inside diameters and correspondingly smaller wall thicknesses. What is needed is a catheter with a construction which provides the requisite structural integrity and lubricity while allowing a larger inside diameter.